Setting Data Path Width - HP 9000 Series 300 Tutorials Manual

Note
Be sure that the timeout limit is set to a value higher than
the longest expected time to complete a transfer. If a normal
transfer takes longer than the timeout limit, the operation is
aborted even though system operation is correct.
Timeout is specified in microseconds (/lsec) in the call to io_ timeout_ctl, but
the actual timeout used and its resolution is system-dependent. The timeout
value is always rounded up to the nearest normal time resolution interval
supported by the system executing the operation. For example, if the available
system resolution is 10 milliseconds and a timeout of 25000 microseconds (25
milliseconds) is requested, the actual timeout value used is 30 milliseconds.
To determine timeout resolution for your system, refer to the appropriate
hardware-specific appendix.
IMPORTANT A timeout value of 0 microseconds is meaningless because
no device can respond with data in less than zero time. For
this reason, the default or a specified timeout value of zero is
treated as a request to disable timeout and any condition that
would normally cause a timeout termination is ignored by the
system, usually causing the program to hang. Specifying a
timeout of zero is not recommended.
Any interface file eid obtained by using the dup(2) system call or inherited
by a fork(2) request shares the same timeout as the original interface file eid
obtained from open(2). If the child process resulting from a fork inherits an
eid then changes the timeout, the eid used by the parent process is likewise
affected.
Setting Data Path Width
When you create a DIL special file and open it for the first time, the data
path width defaults to 8 bits. Once the file is opened, io_width_ctl can be
used to select a new width. Allowable widths vary, depending on the computer
model and interface. Refer to the appropriate hardware-specific appendix to
determine what widths are supported by specific interfaces.
General-Purpose Routines 2-17